Gear reducers are well-known and commonly available mechanical devices for altering the speed and torque of a rotating drive, typically placed between a motor and a mechanically driven device. Gear reducers generally include a housing and an input and output shaft which are rotatably supported by the housing. Reduction gearing inside the housing forms a drive train connecting the input and output shafts and defining the "gear-ratio", that is, the ratio between the angular motion of the input shaft with respect to the angular motion of the output shaft.
Many different gear-ratios are available. For example, the American Gear Manufacturers Association (AGMA) has adopted 13 different standard ratios from 5.062:1 to 57.66:1.
A gear reducer may be shaft mounted, flange mounted or foot mounted, depending on the configuration of the housing. Any gear-ratio may be used with either mounting type resulting in many different possible gear reducer variations. Typically this variety requires that a supplier stock many different gear reducers so as to be able to supply customers with a variety of gear ratios.
With foot mounting, the housing of the gear reducer includes a mounting base which is attached to some fixed support relative to the machinery associated with the gear reducer. With shaft mounting, the housing of the reducer includes a mounting collar that attaches directly to the associated machinery. In either case, the mounting ensures proper alignment between the input and output shaft and the associated machinery during operation of the gear reducer.
Depending on the manufacturer, the position of the output shaft with respect to the mounting base and the location of the mounting holes in the mounting base will vary. For this reason, foot mounted gear reducers of one manufacturer are not generally interchangeable with gear reducers from another manufacturer without extensive modification of the mounting arrangement.